Re: Offset a void pointer

On Thu, 14 Oct 2004 15:11:04 +0100, Richard Fabian <[email protected]> wrote:
> if you are referring to this:
> 
> http://gcc.gnu.org/gcc-3.4/changes.html
> from the section starting:
> "The cast-as-lvalue extension has been removed for C++ and deprecated
> for C and Objective-C. In particular, code like this: "
> 
> then that is just that GCC has caught up with MS compilers in
> dissallowing the implicit lvalue return of standard C style casts
> 
> Still appears to be perfectly legal to cast to an explicit lvalue type...
> 
> Please correct me if i am wrong on this... At least in my head it
> certainly seems to make no sense to take out casting to a modifiable
> type...
> 

Alright, my apologies, for I misunderstood what they meant. The
comments in gcc release notes were only refering to gcc extension of
cast-as-lvalue as in the additional stuff they allowed there, not as
cast-as-lvalue as a whole.

I tried to compile this with gcc 3.4.0:
	void *ptr;
	(char*&)ptr += 5;

and indeed, it worked.

Trying to compile
	void *ptr;
	(char)ptr += 5;

gave the following error message:
"error: ISO C++ forbids cast to non-reference type used as lvalue"

Which confirm that the standard allows using cast as a reference, and
only them, as lvalues, so you were right.

I'll be banging my head on some nearby wall.


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